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Who builds aircraft faster, Boeing or Airbus?
Setting aside recent Boeing MAX crisis and post pandemic manufacturing issues, who was overall delivering aircraft faster before 2019, Boeing or Airbus?
PS: If you want to pick a specific model, Let's consider their most popular version for comparison,  B737 vs A320 .

Whatever the current rate of production for Boeing aircraft is, it is too fast for safety.

unfortunately indeed

@Gabe with their quality standards nowadays, probably building 1 aircraft per month would be too fast.

Airbus claims that it takes 1 month for the final assembly of an A320 and from manufacturing of first part to completed aircraft it takes 1 year. This is probably because Airbus has various factories all across Europe to build the planes.
After the fuselage is brought over by train, Boeing has claimed that it only takes 9 days to assemble the aircraft. They are currently planning to make 42 737s per month from February.
From a pretty long time, Airbus has had an edge over Boeing in terms of A320 per month, currently it seems to be approximately 45-60.
Sources -
Boeing 737 in 9 days after receiving fuselage
Airbus A320 per month figures (Aug 23)
Time taken for A320 manufacturing
PS: I see now that the question was asking about pre-2019 production  rates, from some reasearch I've done it can be seen that Airbus was still a bit ahead of Boeing in 2019 but Boeing was certainly more competitive than it is now.


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How can the Yak-130 fly with blocked engine inlets?
In this Yakovlev Yak-130 youtube video you can see at 2:45 where it closes the inlets(something I've never seen before) and then it does a perfect take off (at 2:58) like there's nothing wrong with closing the inlets.
Can someone explain how is this possible?

The inlets are closed in order to avoid FOD (Foreign Object Damage) when taking off from unprepared fields. When the main inlets close, two other inlets open above the fuselage, as visible in the following photograph (source):

I think that this solution was imposed by the compactness of the airframe and the proximity of the front landing gear to the inlets, which worsen FOD ingestion.
As pointed out by Peter Kämpf, MiG-29 was the first fighter to employ this double inlets system.
Apparently the twin design M-346 by Aermacchi (now Leonardo) doesn't possess this kind of feature (source):

It was also that FOD tolerant features, like intake grilles, was accounted for in Soviet design going way back, partly because of the expected imperatives in wartime, and partly because even in peacetime junk on the pavement was a never ending problem on Soviet bases.

You might want to add the MiG-29 as the first design which used intake covers and overwing intakes for take-off. See here or here for more.

This is mentioned prominently in the Yak-130's Wikipedia page. However: what is the second grill adjacent to the above-wing intakes?

source: Stack Exchange

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What does the letter/number on the nose wheel door means?
Most airliners have different letters/numbers on the nose door.
What is it for?

Related: Why is there an ETOPS marking on the nosewheel door?

It means that there's a runway incursion and 816 is about to land on top of QT. Roll fire trucks!!!

Easy ID the specific airframe by ground crew.
The whole registration ID is way at the back, likely way up on the tail.
What may be on the nose gear door is just the last few numbers/characters of the full reg num. e.g. Lufthanasa D-AIQT shows "QT" on the gear door  (thanks, jcaron). Enough to identify that particular aircraft, to those who it matters to.

same reason some (many?) airlines place that same code over the cockpit windows, for easy identification.

Not just ground crew, all the crew! I’m a pilot, the reg here is the easiest place to look to look when walking up to a plane to check I’ve got the right one, instead of having to walk round to the back to check the tail. Airplanes are usually parked towards the terminal, so having a reg towards the front makes it easy to check when walking up to the aircraft.

But, if you're wearing your fitness tracker, @tedioustortoise, that journey all. the. way. to the back of the plane gets more steps in! :)

It’s probably worth clarifying that the letters/numbers shown there are a part of the full registration IS (aka tail number), so the Lufthansa aircraft on the bottom is D-AIQT, and shows QT on the nose wheel doors.

@tedioustortoise Are the last 2 characters always unique enough to ensure you never jump into the wrong aircraft?

@EndAnti-SemiticHate yes it’s fine. You will then check the full reg on the flight deck where it is placarded.

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Why there is only Boeing and Airbus?
Amidst all these new scandals with Boeing and unbelievable/disgusting safety situations like the  example of the hidden camera report long time ago, and knowing that airlines only have Boeing or Airbus to purchase from and both with long waiting list, I wonder why don't we have other big airplane manufacturing companies?
I mean we have so many different manufacturing companies on the general aviation (yes I know they are smaller/"simpler") but I mean even on regional aircraft, which are closer in size to the big airliners, there are decent options(ATR, Dash, Embraer, Bae, Bombardier, etc).
Why there is only this BoeingAirbus duopoly, is it a economic reason, is it a regulatory reason, or is it a engineering complexity, what is it, what is the reason?
PS: Yes, there is Comac and Tupolev but those probably are never going to sell in the US/Europe. The question is towards the American / European / and similar markets.

All the other older major aircraft manufacturers got bought up by either Boeing or Airbus. Even Airbus bought Bombardier's CSeries airliner a few years back as the A220.

Some other large manufacturers of aircraft are Embraer (Brazil), Antonov (Ukraine), and United Aircraft Corporation (Russia). UAC was formed by a compulsory merger of Russia's aircraft manufacturers. There's also some other smaller manufactures in other countries.

Do you have a few tens of billions of dollars laying about so you can start up a competitor? Yeah, neither does anyone else. In America, at least (I don't know about rules in the EU/UK) anyone is free to start up a company to build something, but it's not a cheap process for any manufacturing concern, especially one as tightly regulated as aviation. Why aren't there many/any startup GA manufacturers? Same reasons, just on a (somewhat) smaller scale.

Boeing and Airbus are not isolated aircraft manufacturers, they belong to groups which also work in space and defense industries, e.g. "Airbus" is a branch of Airbus Group, formerly European Aeronautic Defence and Space (EADS).

Embraer is worth mentioning for its success, and on the other hand, there's Mitsubishi who tried hard to enter the market.

https://en.wikipedia.org/wiki/Saturn_Corporation "Saturn was founded as a private, employee-owned company, by former GM leadership. They remained private until GM bought them out, and effectively "rewrote" company history." "the project was too ambitious, as "everything at Saturn is new: the car, the plant, the workforce, the dealer network and the manufacturing process. Not even Toyota, a highly successful and experienced automaker, tackles more than two new items on any single project.""

There are lots of airplane manufacturers right? https://en.wikipedia.org/wiki/Aerospace_manufacturer#Largest_aerospace_companies

It's the same tendency for consolidation that happens in all kinds of industries, once the stronger players gain the ability to expand by swallowing up the smaller players. Which usually starts because there are simply too many, then the pendulum swings until there are too few.
Bombardier made a play at muscling in on the Big Twins' lower tier with the C-series, but the costs drove the company to the edge of insolvency. The company was forced to give the program away to Airbus after the exclusion from the US market that resulted from Boeing lobbying.
The C-series having sucked all the money out of the Regional Jet program, Bombardier ended up getting out of the airline business totally by unloading the rights to the CRJs to Mitsubishi, abandoning that market to Embraer, and is now back to being a business jet manufacturer as it was in the 80s.
It's a shame in a way for an observer in Canada, because at the technical/operational level, the C-Series/A220 has succeeded beyond anyone's hopes back when it was in development.

Yeah, the CRJ is really an awesome aircraft, I've been in one of them, is so smooth, fast and nimble. Do you think the government should try to prohibit the acquisition / merger of manufacturers just like they tried to do with the airlines.

@Gabe in the US there are anti-monopoly laws that the FTC gets involved in for major company acquisitions. Some may say that it hasn't worked in the case of Boeing... Then again, too much government involvement isn't always great, either.

Only if the acquisition is by a hostile power IMO, or there is some compelling national interest, where the govt takeover required and all the negative fallout from that is worth it. Generally, state run businesses don't end well. The Fed Govt took over DeHavilland Canada from Hawker Siddley Group in the 70s as it was about to cancel Dash 7 development, eventually unloading it to Boeing just after the Dash 8 entered service, in a bizarre marriage, who unloaded it to the Prov government, who then unloaded it to Bombardier, who've now sold it to Viking.

The one thing that large companies want is more government intervention. To prevent competition... Big companies have deep pockets. Politicians can't be expected to live on a government salary...

@Questor never thought about it in that way, but yeah makes sense now that you say it. I can see this is not a aviation issue, is a broken system issue. sad.

@Gabe Part of it is a broken system, but part of it is also just a function of the costs involved. Commercial jetliners are expensive to develop, certify, and produce. Even with more limited regulation and no lobbying by existing players, it’s not a market that it’s easy to even consider competing in. You can see the same effect in most other industries where total cost from design to production is measured in the billions of USD (for an extreme example, see EUV silicon phtolithography systems, ASML is the only supplier in the world for those).

Off the top of my head I would say (and it's definitely not going to be a thorough answer):
Time, money, tools and people.
Let's use the A350 as an example:

its design started as a clean sheet at the beginning of 2006 (actually 2004 if we take into account Airbus' initial idea to propose a simpler improved version of its A330); the first commercial flight was beginning 2015, i.e. 9 (or 11) years later;
total development cost summed up to around 15 billion US$ - 12 billion €, up from the initial estimation of 4 billion €;
Airbus employs some 110 thousand people; yes sure, not all of them worked on the development of the A350 but you also need people to certify, build and sell the aircraft, to handle external partners, people and customers and many other things not directly related to the physical aircraft.

An hypothetical startup willing to compete with Airbus (or Boeing) would need to find at least the same resources, actually more since Airbus has already people, tools, facilities, processes, customers, partners...

Aircraft manufacturing, railways, shipyards, electrical distribution, roads, satellite launch services, CPU manufacturing, telecommunications networks ... all these businesses have very little competition.  The cause is the same for all:  getting started in the business is very expensive.
Roads, passenger rail, passenger air travel to smaller cities all rely on government subsidies.  Nobody wants to compete in those money losing businesses.  Boeing gets subsidies from the United States.  Airbus gets subsidies from the European Union.  A new manufacturer would be unlikely to get much from governments.

One can look the other way round: we are pretty much happy to have two market players in a market that strongly favors mergers and other consolidation paths. Big number investments, slow turnover, technology complexity, and heavy regulations are not the best place for small independent businesses and startups.
The good thing is that those two market players ended up in the two biggest economy spaces in the world - the US and the EU.
Both Airbus and Boeing are deep into "too big to fail" and "not in my term" areas for their corresponding governing bodies. Allowing a hypothetical merger or buyout will be a political suicide for whoever holds the corresponding office at either side.

Yes, the political importance of keeping some companies afloat is a key factor (ie indirect protectionism). You see this in how smaller car manufacturers during a downturn readily succumb or are taken over when not provided with government protection (SAAB, Volvo), whereas larger protected ones (the big three) lumber on.

Basically we have two players because a monopoly would be bad, so the US is propping up Boeing and the EU is propping up Airbus.


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Cruise with a single engine in a twin, good idea?
Airlines are looking to lower costs every single day.
I wonder if it makes economic sense (fuel costs) to operate a airliner using only one engine during cruise, while keeping the second engine at idle in case of engine failure.
Would it make sense, would it be the same, or would it be worse?
Note that this would only apply to the cruise phase. TO/GA and landing would use both engines as normal for obvious reasons.

Very related: Does one-engine cruise consume less fuel than two-engine cruise?

Using actual numbers, a modern A350 at fairly heavy weight of 250 tons will have a specific range (distance travelled over burnt fuel) of approximately 77NM/1000kg at optimum cruise altitude of 37000ft. If one engine is shutdown, the performance is not adequate to maintain that altitude and aircraft is forced to descent to an altitude around 21000ft where density of air and thus drag is higher. The specific range drops down to around 60NM/1000kg so it is not economical even fuel consumption wise. On top of that the ground speed is roughly halved which doubles the travel time between two destinations, basically halving the amount the number of profitable tickets an airline would be able to sell.
And that is assuming we ignore safety, risking loss of total thrust in case of failure of the remaining engine - among several other less obvious risks such as secondary system failures and contrallability of aircraft.

I have accepted your answer since it betters addresses my initial question. Thanks for that info.

A twin engine aircraft with one engine operating (OEI) suffers considerable drag penalties.  First, there is the drag of the windmilling engine.  Since the engine is likely out on the wing, it causes a significant moment that requires rudder and aileron deflection to offset.
Best range for a transport aircraft occurs at high speed -- approximated by best $M\,L/D$.  We usually cruise a little faster than that because we value time.  Consequently, we usually cruise at pretty high throttle and the TSFC is pretty good.
Your suggestion would make more sense if we were flying for best endurance -- where we fly slower, require less throttle, and would incur a greater penalty for low TSFC from operating at low part-power.
That said, there is this proposal for a two-engine aircraft (with different sized engines) that would turn on and off depending on the phase of flight.
I believe the four-engined P3 Orion would shut down one engine during cruise.
Also, there are three-engined helicopters that shut down one engine during cruise to get longer range.
Edit below:
A jet engine has a characteristic that we call a 'thrust hook'.  It is how the TSFC (y-axis) varies with thrust (x-axis) as throttle is varied at a single flight condition (Mach, altitude).
In this case, the thrust axis has been normalized by the sea level static (SLS) rated thrust.  The flight condition is typical high speed cruise.
At this flight condition, maximum throttle only delivers about 27% of SLS rated thrust.  This is due to thrust lapse.
The shape of the thrust hooks is what is important.  They usually have a relatively flat region near high throttle settings.  This is observed from about alpha=0.17 to 0.25.
Then, there is a fuel flow penalty at very high throttle -- from 0.25 to 0.27 (some engines don't really have much here).
On the other hand, for fighter engines, this would be where afterburners kick in -- the thrust jump would be much larger, but the TSFC jump is crazy too!
More interesting to us is the gradual (but steep) TSFC penalty at low part power (alpha less than 0.17) -- getting really bad at flight idle.
Lets say an aircraft was at a flight condition where flying with both engines operating required alpha=0.09 (TSFC=0.72).  Instead it could operate on a single engine at alpha=0.18 which would give TSFC=0.65.  Which is about a 10% improvement.
So, you're looking for a situation where the 10% fuel flow improvement is larger than whatever drag penalty you would have.
Many loitering missions involve flying in circles.  For example, a long endurance drone that wants to continuously monitor a certain region of the world.

If during part of a flight, a plane wasn't going to be traversing any useful distance but just circling to remain airborne, e.g. because one was near the destination but couldn't land immediately, how would endurance using one engine at relatively open throttle compare with endurance using  both engines throttled back?  If the plane is supposed to fly in a circle, one might not need much rudder to compensate for asymmetric thrust.

"If the plane is supposed to fly in a circle, one might not need much rudder to compensate for asymmetric thrust."  That's not now a coordinated turn works.  With asymmetric thrust the need for rudder doesn't go away because you have an angle of bank.

@MichaelHall coordinated turn just means there is no slip. If you have asymmetric thrust and use the ailerons to eliminate the forward slip induced by it, then you're doing a turn and are in coordinated flight, so it's a bona fide coordinated turn. Whether it's as efficient as a conventional rudder-induced coordinated turn is another matter, but I suppose it would indeed be relatively more efficient than rudder-corrected forward flight with asymmetric thrust.

@leftaroundabout, OK you got me...  Yes, I suppose you could counter the asymmetrical thrust with adverse yaw from the ailerons, but only in one direction.  The point is that you still have to counter it with a draggy solution.

@leftaroundabout The implication of your proposal is that the adverse yaw produced by the ailerons is about the same magnitude as the yaw produced by having only one engine producing thrust, but I believe that, except perhaps for aircraft with engines near the centerline, asymmetric thrust calls for significantly more rudder than does adverse yaw.

@leftaroundabout --  "If you have asymmetric thrust and use the ailerons to eliminate the forward slip induced by it, then you're doing a turn and are in coordinated flight" - I think you are making an error here.  If the forward slip is eliminated (as far as the "yaw string" is concerned), why would the ailerons be signficantly deflected, regardless of whether you are circling or flying straight?  The ideal condition would be just enough rudder to fully streamline the fuselage (and center the yaw string) (but not fully center the ball), regardless of whether circling or flying straight.

@leftaroundabout -- (ctd) In that condition, the ailerons should be nearly centered, regardless of whether you are circling or flying straight. For more, see https://aviation.stackexchange.com/a/91153/34686, and other related answers to that question.  As far as the circling case goes, look specifically at the paragraph near the end of that starts "Maybe it would help to explain it this way:".  A different bank angle will be required to circle than to fly straight, with yaw string centered in each case, but rudder deflection should be about same, and ailerons nearly centered, in either case.

@leftaroundabout -- (ctd) If, after applying exactly enough rudder to center the yaw string, you opt to skip the step in that paragraph mentioned above that states "then, while keeping the ball in that position, bank as needed toward the good engine to stop any turning tendency and hold the heading constant", you will end up slowly circling (toward the stopped engine) with wings completely level, but the rudder will still be strongly deflected, and the ailerons will be centered or nearly so.

@leftaroundabout -- basically what I'm saying is that if you need a significant aileron deflection just to hold a constant bank angle, be that 0 degrees or otherwise, then you are not in "coordinated" flight at least as defined by the yaw string. Rather, you are fighting the roll torque created by slip-roll coupling. You can say it is "coordinated" because the ball is centered, if you want to, but the expectation would be that efficiency would be low, because the yaw string is not centered, showing that the relative wind / airflow is striking one side of the fuselage and vertical fin.

@leftroundabout -- More to the point, it takes a bit more rudder to fully center the ball, than it does to center the yaw string and leave the ball a bit off center.  That's using the ailerons as needed to hold a constant bank angle, which in the case where the ball was centered not the ys, would typically require some aileron against the rudder, because from the perspective of the yaw string, you are slipping.  Being in a turn rather than linear flight isn't going to change that.  So the idea of somehow producing coordinated flight w/ ailerons but not using rudder isn't going to work.

Re "basically what I'm saying is that if you need a significant aileron deflection just to hold a constant bank angle, be that 0 degrees or otherwise, then you are not in "coordinated" flight at least as defined by the yaw string."-- some of these comments are for an ideal case where there is no propwash over wings.  Adding propwash complicates things, but the same basic relationships still apply, and you'll still find that there's no case where adverse yaw from the ailerons somehow allows you to center the ball, or the yaw string, whichever you prefer, while not also applying lots of rudder.


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How did this F/A-18's execute a "low-boom maneuver"?
The Engadget article NASA will publicly test quiet supersonic technology in November says:

The administration plans to conduct a series of public tests around the coastal city of Galveston in November. The F/A-18 Hornet aircraft at the heart of the tests will perform dive maneuvers that produce louder sonic booms out at sea, while quieter sonic "thumps" will take place over Galveston proper. After that, "at least" 500 local volunteers will provide feedback on what they heard, while audio sensors will provide more definitive noise readings.

and links to the NASA YouTube video NASA Social: Low-Boom Maneuver:

This footage is from a NASA Social event at Armstrong Flight Research Center during which the F/A-18 was flown to produce a regular sonic boom and then a low “boom” by performing the dive maneuver described in this story. The normal sonic double boom occurs at 0:43. The low “boom” occurs at 02:34. The rest of the footage includes a flyby, planes on the ground with NASA Social participants, a visit to the Ikhana UAS and a pilot signing.

Question: What would be a simple way to understand what a "low-boom maneuver" is, and how would an F/A-18 execute it? In this case would it require any modification of the Hornet's configuration?
Is producing the boom during a dive of particular relevance to the reduction in sound level, or is this just a convenient way to do this particular experiment? Since the sound level as well as the reduction of the level for the low-boom maneuver at ground level may have a directional dependence, I'm wondering if the direction of the dive needed to be carefully planned to be representative of how the reduction would work for civilian air travel boom reduction, where dives are (thankfully) less frequent.

By flying straight up before exceeding Mach 1, to spread the boom more widely.
The commentary says: at 2:10, "pull up" and the smoke trail suddenly points upwards; "[2:16] subsonic below thirty thousand feet," "point zero nine Mach [for?]ty thousand [feet?], thump, copy one point zero nine Mach, more thumps, [2:39] one point zero eight Mach."
In the dive at 2:02 he's "supersonic" already before "he's pulling up."  The dive is only to build up enough speed so that the subsequent climb starts fast enough to eventually exceed Mach 1.
Heard from the ground, what are the thumps at 2:30?  Forty thousand feet up is eight miles, roughly 45 degrees above the horizon; so as many miles horizontal, say twelve miles total.  The speed of sound is 4.5 seconds per mile, so the lag from video to audio is 54 seconds.  2:05 is when the dive is "supersonic right now." The thump at 1:36 shows that the horizontal approach to the dive was supersonic.
Faint thumps are at 3:01 and 3:15, thus generated at 2:07 and 2:21.  2:07 is just after ascent starts: maybe parts of the airframe exceeded Mach 1 in that high-G maneuver.  2:21 is mid-ascent, thus the cause of the intended low-boom maneuver, between the radio chatter that says subsonic at 2:16 and supersonic at 2:39.

Okay, now let's hope they'll do it a bit differently on commercial supersonic flights! ;-)

What might be the purpose of this test?

To measure how much quieter (numerically) and how less annoying (by interviewing witnesses) a sonic boom could be, to support current research into commercial supersonic flight over land.  https://www.ainonline.com/aviation-news/business-aviation/2020-04-01/faa-proposes-noise-standards-supersonic-aircraft

I did some reading and this is what I could find out so far:
https://www.nasa.gov/aero/nasa-prepares-to-go-public-with-quiet-supersonic-tech
This article is similar to the Engagdet one but goes into slightly more detail(though not enough for a proper explanation) about the dive maneuver.
However, Lockheed Martin is in the process of designing and building a low sonic boom demonstrator, slated to fly in 2021. The wikipedia page says that to prevent sonic booms from building up, the aircraft will have a long slender body and canards (thought the Concorde had these as well, so I'm not sure what the difference is). They will probably add canards to the F/A-18.
The dive maneuver happens in such a way that while the sonic booms directly underneath the aircraft are strengthened, there is a secondary pair of sonic booms created further ahead that are weaker, giving quiet thumps instead.
Hope this helps.

It sure does help, thank you!

No problem. If you can find any more info as well, let me know. This stuff is cool as hell.

I wonder if there is more information about this available now?

http://mil-embedded.com/news/avionics-from-collins-aerospace-will-ride-on-nasas-quesst-demonstrator-aircraft/ https://www.aerospacemanufacturinganddesign.com/article/lockheed-begins-manufacturing-nasa-x59-quesst-112718/ found these two articles so far. Most recent ones I could find. Progress is being made on the aircraft which is nice to see.

It would be great to hear more about the "low-boom maneuver" itself, so far I still can't find anything specific.

I'm wagering that they are keeping it under wraps since it's still in its infancy as a technology and no one really has played around much with it before. Since Lockheed Martin and NASA are at the forefront of this research, they will keep things quiet for a while.

aha!: images, videos, and news I don't understand this stuff, maybe you can make some sense from it?

To elicit low sonic booms, commonly also described as sonic thumps, the F-18 first ascends to near its maximum altitude (40-50,000 feet). Once the height is reached the plane turns upside down and falls to a much lower height (15-20,000 ft), while breaking the mach border. The overall procedure is depicted on the QSF 18 "Quiet Sonic Flights" research crew patch from NASA.
I think that turning the plane around on its way to the ground achieves the rear fins of the plane distorting the sound waves on their way to the ground (in contrast to a flat belly of the usual plane, which reflects "hard" N-Waves - the sound signature of a conventional sonic boom on the ground roughly looks like the letter "N" to the ground).
The pull up manoeuvre observed wasn't the actual supersonic transistion, but the exit from the manoeuvre alltogether. You can find a detailed description of the whole procedure in Sullivan et al's paper "Human Response to Low-Intensity Sonic Booms Heard Indoors and Outdoors".


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Are all the Airbus A380's 16 exits designed for everyday use?
Are all the Airbus A380's 16 exits designed or everyday use for embarking and disembarking the aircraft, or are some specifically designed for use as emergency exits, such that opening any of those designated as emergency exits would require specialists to put them back in place?
In other words do all have hinges for everyday use?


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Why doesn't the landing gear get raised on the first flight of a new airplane?

This image shows the A350 first takeoff high in the air and the landing gear is still down. Why didn't they retract it?

Because they might not come down again :-)

Perhaps they are also testing gear-down performance?

Pondlfe is (at least partially) correct.

Test flying is thoroughly planned, and of the many things to test during development, the landing gear is just a minor part. In the first flight the goal is to check out basic functionality and how well the low-speed performance was predicted. The landing gear can wait for one of the later flights. You can see in the photo of the A350 that the slats are extended and the flaps are in take-off position. The pilots are busy testing handling in take-off configuration, and for that the gear must be down. You can be sure that they also tested the landing configuration at altitude before going down to land.
Generally, the tested envelope of the aircraft will be expanded step by step. Since every flight will contain a take-off segment, it is prudent to check out this part of the envelope first. Once the low-speed regime is tested, consecutive flights will take the aircraft to higher speeds, and only then will it be necessary to retract the gear.
Also, the first flight of a newly developed aircraft has become a ceremonial affair. After having spent hundreds of millions of dollars or euro, and with all the media attention, nobody wants to live through the embarrassement of a gear failure on occasion of the first flight.
This was not always the case. The F-100 went supersonic on its second flight; taking this kind of risk would be unimaginable today without the pressure of an arms race.

Aircraft flight testing a rigorous and elaborate affair, with the aircraft first tested at low dynamic pressures and as the performance data is received and analyzed, the flight envelope is expanded slowly.
During the first flight of test aircraft, the approach is to take minimal risk. Keeping the landing gear extended serves two functions:

Landing gear systems are very complex in themselves and it serves no purpose to check them in the first flight. There is a possibility that they may not retract or may not extend after retracting. As Peter pointed out, this is not a good thing to happen in first flight.
Also, in case the aircraft has to land in case of any emergency, it is better to keep the landing gear in extended position.

There are a few cases in which the landing gear malfunctioned during the first flight. In the first flight of YF-22, which went on to become the F-22, the landing gear retraction was not planned. However, when it was tried in subsequent flights, the gear did not retract due to software issues. However, it has to be noted that the while retraction was software controlled, extension was hardwired for safety.
Another case of landing gear failure is the NASA dream chaser plane, which suffered landing gear malfunction in its first free flight.

As the aircraft approached the runway, the left landing gear failed to deploy, and the aircraft skidded off the runway and was damaged.

I always check my landing gear before a fist fight.

The simple and easy answer is that the first of any new aircraft design, no matter how well-engineered, well-constructed and/or derivative of earlier designs, is a complete unknown. The first flight is always gear-down because if there's any problem, the test pilot/crew needs to be able to get the plane back down on the ground without having to deal with any additional issues (like not being able to get the gear back down). Gear extension, retraction and emergency release are all thoroughly tested many, many times with the aircraft on a lift prior to the first flight, but still, anything can happen, and better safe than sorry (especially in a civilian aircraft design without an ejection system).

Right, the gear is tested on the ground, but without air loads. Simple elastic deformation due to flight loads can render the gear mechanism inoperable if the designers did not think of this.

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Is this XKCD comic list about autogyro features accurate?
I recently came across this XKCD comic which gives you a number of facts about autogyros:

Image is copyright XKCD, licensed under CC 2.5 BY-NC
I'm not sure if this is satirical or really drawing attention to some very odd real-world facts, or a mix of the two.
Statements:

Looks like a helicopter, but is nothing like a helicopter
Flies like a plane but is nothing like a plane
Cheap
Needs a runway to take off, but not a long one
Can land vertically
Cannot hover
Big blade on top is not powered […]
Never stalls
Sort of like a powered parachute
[…] usually homemade.
Common in Europe. (I'm fairly sure I've never seen one in the UK)
Can often be flown without a licence

Are these things all true? How do they actually work?

While definitely niche, they're pretty common in the UK and most busy airfields with have them as relatively regular visitors.

See also https://aviation.stackexchange.com/questions/49865/why-does-this-xkcd-comic-say-that-autogyros-will-crash-if-the-pilot-reacts-to-a

Europe is a big place. For example, the statement "German is commonly spoken in Europe" is clearly true, despite the fact that I can't remember when I last heard it being spoken in the UK.

When discussing details of XKCD, I can highly recommend the community-driven Explain XKCD wiki project. For this specific comic, see here: http://www.explainxkcd.com/wiki/index.php/1972

Possible duplicate of Why does this XKCD comic say that autogyros will crash if the pilot reacts to a stall like in a normal airplane?

You left off the final statement, which abuses the word "instinctively".  In fact, what anyone instinctively does in a stall is to pull back on the stick/yoke to try to climb faster, which is what caused the stall in the first place.  Pilots have to be trained to recognize a stall for what it is, and fight their instinct to pull back, and instead push forward until they get out of the stall. This is similar to drivers learning to steer into a skid.
No matter how much one practices these things, they don't truly become instinct.  They can, however, become automatic.

@MontyHarder There's a whole other question on just that one point. I decided not to step on their toes.

@Harper why do you think this is a duplicate?

@Federico Some sort of consolidation is called for, or else this will get silly fast.

Flies like a plane.

To a certain extent in that the controls are plane-like, you do not have helicopter controls (no cyclic, etc.), but you also do not have wing control surfaces, so in some respects like a plane, but not exactly.

Big blade on top is not powered.

True, the blades are unpowered; they rotate due to the wind. Some autogyros use power to rotate the blade to speed before take off, but the power is removed for flight.

Never stalls.

You can put it into a stall attitude, but it self-corrects; it is basically a rotating parachute.The fatal mistake that pilots made with early autogyros was that when they entered stall conditions they instinctively pushed forward on the stick which resulted in the 'fuselage' tipping forward and the blades chopping off the tail. There have been a few fatalities this way.

Sort of like a powered parachute.

Fairly good description. It is more like a powered paraglider than a helicopter or plane.

Common in Europe (I'm fairly sure I've never seen one in the UK)

Maybe this should be more common in Europe. They are still uncommon in Europe, but they are more common in Europe than the US. Wallis Autogyros used to make them in the UK in the 1960s. Check out the Bond film "You Only Live Twice" for one in action (ignore the missiles, etc.; they are not standard fit on autogyros).

Can often be flown without a licence.

Not in anyplace I have flown in Europe. The US may be different.

Thanks for alerting me to the fact missiles are not standard on Autocyros ;)

"Cannot hover" is true because the rotors require wind (forward motion) to drive them. "Can land vertically" is true I think. I've certainly seen one land with a very, very short stopping distance ( ten feet).

Note, of course the statement made in the comic is that it "flies like a plane but is nothing like a plane", so it sounds like the full statement is pretty accurate.

Chopping off the tail? Really?...

Fun fact, the autogyro in You Only Live Twice was called "Little Nellie".

Yes. Rotor strike is not uncommon. There have been many cases of the rotors striking the rudder or the propeller.
https://www.gov.uk/aaib-reports/rotorsport-uk-mtosport-g-paff-28-december-2013
https://assets.publishing.service.gov.uk/media/5422efb3e5274a13170002af/Air_Commander_532_Elite_autogyro__G-BPJY_07-89.pdf
https://aviation-safety.net/wikibase/wiki.php?id=19519

"gnore the missiles etc, they are not standard fit on autogyros" - Dammit

As mentioned in the answers to the other recent question about this comic, the "fatal mistake" is not about rotor/tail strikes but is about de-loading the rotor when a pilot pitches forward. Without load, the rotor stops spinning and you lose lift.

Many of the them in the USA qualify as ultralights.  Those don't need a traditional Airman's Certificate, so the last attribute is 'technically correct.'  Many of the ones built in Europe, these days, qualify as a Light Sport Aircraft.  Those do need an LSA certificate.

What about, "Needs a runway to take off" and "Can land vertically"? As far as I know it can only land vertically by flying into a heavy wind, matching airspeed to windspeed. But with the same technique, it could also take off vertically...

A lot of the points are technically possible but not practical. I can take off vertically in my glider but not for very long and not safely before the drag causes me to fall out the sky. I can, if lucky, find some good ridge lift and sit motionless relative to the ground on top of a rising wave of air by balancing the drag from the wind with the forward speed caused by the fall and if the lift exceeds the vertical fall you rise. Technically if all these come together and I am sitting on the ground in the sweet sport I can take off vertically. Similar to autogyros. Possible but not practical.

" (ignore the missiles etc, they are not standard fit on autogyros)" - DAMN. Really? Boring.

"I'm fairly sure I've never seen one in the UK" I have friends who lived near "Wing Commander Wallis," and we would see him exercising his collection most weekends in the summer, up until he was at least well into his eighties

The absence of the missiles is a violation of my second amendment rights.

What about hovering? I thought you needed to be moving forward to keep top rotor moving.

The "needs a runway to take off" statement is historically true of most autogyros, but many modern ones can take off vertically. It's called a "jump takeoff."
It works by flattening the blade pitch so no lift is generated, coupling the engine to the rotor, and spinning the rotor up to a higher-than-normal RPM. Then the engine is decoupled, and at the same time the blades return to normal pitch. This uses the stored energy in the rapidly-spinning rotor to pull the autogyro upward. From there it transitions to forward flight before it has time to settle to the ground again.

https://youtu.be/3RPYWmdv174?t=48

Arguably for as long as the main rotor is powered, and while that residual momentum remains after it’s removed, the craft as a whole isn’t really an autogyro, since the unpowered main rotor is kind of a distinguishing feature on an autogyro. Only once it starts going forward does it start acting like—read: being—an autogyro.

@spender your link fails with a privacy error for me

@KRyan: To argue in the other direction, a major distinction of an autogyro is that the rotor doesn't produce torque in flight thanks to being unpowered. As long as the rotor is only powered while the craft sits solidly on the runway and can dump excess angular momentum into the ground, having energy stored in the rotor afterwards could well be considered secondary in importance.

@HenningMakholm Interesting point! That almost sounds like it would seem different depending on your perspective—to the engineer who doesn’t have to figure out handling the angular momentum, it’s always an autogyro. To the pilot, though, powering the main rotor for lift-off induces very un-autogyro-like behavior, and therefore (again arguably) means it doesn’t really qualify as one for that time.

Re the "Can often be flown without a license" this is true in the US for certain types of gyro - small, one-person craft which are classed as part 103 aircraft. All the more modern, useful ones that carry two people and have more powerful engines require a license.
Re the "safe unless..." piece, this is kinda true. What Randall means is that most pilots, in situations where they are concerned about possible stalls, will push the stick forwards. If you do this in a gyro, it can unweight the gyro to the point where air is no longer flowing up through the rotor, which will then slow down - quickly. If it loses sufficient momentum (and this can happen very fast), it will stop AND IT WILL NOT START AGAIN. This is because although you will be falling and air will start rushing up through it again, it doesn't happen in a way that allows the blade to start rotating correctly. So gyro pilots have to learn not to do this.
I have 600 hrs in gyros (1200 total) and when I take pilots up they always marvel at the gyro's ability to slow to zero airspeed and its incredible turning radius, but they're always nervous when I pitch up steeply - always have to explain what I'm doing first!

Wow! It looks like you’ve joined this area of SE just to give that interesting and informative answer. Thank you very much!

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
Why does the ICAO alphabet use "Charlie" for C?
Why does the ICAO alphabet use "Charlie" for C? Specifically, why choose "Charlie", which has a "Ch" sound, rather than a word with the hard "C" such as "Carl"?
A cursory Googling turns up nothing.

I voted to close this, it should be reworded to include the entire NATO alphabet otherwise we are going to have 25 more questions on the subject. The entire NATO alphabet is discussed with great detail and analysis of each letter at https://en.wikipedia.org/wiki/NATO_phonetic_alphabet

A: aye. B: bee. C: cerise. E: eye. G: gnat. H: honour. K: knee/knife. O: oestrogen. P: pneumatic. etc.

If you are from eastern Europe you would spell "Carl" with a K. Karl Marx, karl Benz (Mercedes) Karl Dönitz, a town in Rhineland, Germany etc. etc. etc.

note that C is pronounced like /tʃ/ or /ts/ in many languages, so Ch is almost the same as C

There are only two letters that have a single syllable: Golf and Mike. The majority have two, with some having three. Single syllable codes should be seen as the exception. The linked article says it's not possible to change one letter without reviewing (and possibly changing) the entire alphabet.

The 'ch' in 'charlie' is a quite unique sound, in contrast to the 'z' in 'zulu' and the 's' in 'sierra'. Thus, 'charlie' seems to be a pretty good choice, since in a spelling alphabet you aim for unambiguousness.

I sense some other 25 questions coming in

English pronunciation is a mess. It's because English is a mixture of German, French and Latin, boiled since ages.

@ElmoVanKielmo and others ;)

Because he prefers that to "Chuck" or "Charles," obviously.

I prefer the Irish (insert your region of choice here) Phonetic Alphabet. It starts Able, Babble, Cable, Dabble, Enable, Fable, Gobble, Hobble ... I'm sure you can continue it.

The one I always wondered about was "delta" being that there is a callsign Delta. I've heard people use "Dixie" for D before.

How could Cable sound different than Kable? Or perhaps Cable & Sable?

@TomMcW That use case is well explained in the Wikipedia article.

Much information about the selection process and how it worked, and why "coca" was replaced with "Charlie", can be found in this paper on the topic: https://www.governmentattic.org/4docs/ICAO-WordSpellingAlphabet_1959.pdf - existing answers already partially reproduce the information therein.

ICAO is a phonetic alphabet, so it's all about sounds. English language doesn't have a distinct sound for singular letter "C". You're proposing "Carl", but it's pronounced kɑɹl̩ - with K. Other option would be "cent", but this one is pronounced sɛnt - with S.
"Ch" as in Charlie (ˈtʃɑːli) is the only C that sounds (tʃ) distinctively and can be recognized as "C" without any doubt. The fact that's not a singular C but a part of digraph is not relevant. The clarity of the message is.

This answer is exactly the same as CrossRoads answer.

@CJDennis although the examples make it much easier to understand.

Hard C sounds too much like K.  Ch (Charlie) will not be confused with K (Kilo). And soft C sounds too much like S (Sierra).

Previous names were: Canada, Casablanca, and Coco (or Coca) before finally settling on Charlie. It is required that the name start with the letter it represents, but not having a sound conflict with another name (although a good idea) is not required.

Non-English speakers (especially Germans) or just people who are bad at English spelling might spell "Carl" as "Karl".  There's no other way to spell "Charlie."

Wikipedia says "The Allied military radiotelephone spelling alphabets were created prior to World War I and evolved separately in the United States and the United Kingdom—and separately among the individual military services in the two countries—until being merged during World War II. The last WWII spelling alphabet continued to be used through the Korean War, being replaced in 1956 as a result of both countries adopting the ICAO/ITU Radiotelephony Spelling Alphabet, with the Allied nations calling their usage the "NATO Phonetic Alphabet"." with Cast, Canteen, Chain, and Cork used earlier.

@Jeffiekins: actually, "Czarli" if you were from Poland and knew zero foreign languages, but that still makes 'c' ;) OTOH, if an english-speaker doesn't know this name and overthinks it, he could take it as slavic and write "Tcharlie" - see "Tchaikovsky" (Czajkowski). I bet there are many other ways you could write the sounds of "Charlie" in English

....aaand I've just learnt that currently preferred spelling of Чайковский would be Chajkovskij or Chaykovskiy, while Tchaikovsky is traditional spelling, kept just because we're used to writing it like that. Well.. I can't argue with it, "Chaykovskiy" looks more natural to me, much more that some idiotisms like "voivodeship"..

Cocoa could be confused with Ko-ko, the Mikado character.  The country name Canada is probably well enough known to avoid confusion, but may be perceived as being North-American-centric.  Casablanca seems rather long.

For the same reason we use niner for nine. The phonetic alphabet took a lot into consideration when they were choosing words including how words are pronounced with different accents. "Charlie" like all the other words was likely chosen due to its unique pronunciation across dialects. It is also a nice short two syllable word.


text:
Why were early aviators' trousers flared at the thigh?
For example, these dapper outfits:

(Credit History Bunker)
What purpose does the extra volume down to the knee serve? Why don't modern pilots wear similar jodhpurs?

Are you sure they're not just the style of the day? More specifically, the military style, and that many pilots may have been serving or ex-military?

Because you can't touch this.

@Jamiec Clearly OP is not sure .... I assume that's why they're asking ;)

Classy looking pants.

"It's called fashion, look it up"  -  fashion blogger Nicky Ottav,

It's not too hard to figure out.  Wikipedia says Jodhpurs originated from India where they were part fashion and part practicality (the loose fit in the upper half for horse riding comfort) and evolved into the uniform of most western cavalry officers by the turn of the century.
And, in WWI, where did most, or at least a lot, of the pilots come from in the early days?  Cavalry.

Jodpurs are tight-fitting. Those in the question are "plus-fours", I think.

@pjc50 Modern jodhpurs are tight fitting, but unlike the original design they are made of stretch fabric.

The fact that you spend a lot of time sitting with knees bent both on a horse and in a plane may be relevant

@pjc50: Those are not plus-fours. Plus-fours are breeches or trousers that extend 4 inches below the knee.

Convincing but condescending. Accepted. Never change, StackExchange.


text:
Why did this 737 not take off on first attempt?
This video shows a 737 'near miss' takeoff. I'm curious as to why the aircraft did not take off as expected, i.e. is there anything obvious from the video?

I'm assuming the speed and payload would have been within the expected limits, so wondering if someone can explain what happened.

I did notice the air crew didn't have flaps set. They appear to be at 0°. If they calculated their Vr speed for 15° flaps, then they would have rotated too early.

One thing I'd like to add: while the crew may have messed up in some way, once they realized they didn't have enough speed to take off, they got back on the ground and accelerated enough until they could. There are probably a couple of accidents that could have been avoided had the crew had the presence of mind to do that. I thought that was some pretty quick thinking. I'd love to hear the CVR recording.

Noted that there was a lot of wind and a fairly significant gradient (judging by the landing observed before the 737 takeoff).  The pilots did a great job recognizing and reacting.  3rd try was a charm.

Video by Mentour Pilot analysing this incident: YouTube

It looks to me like they also had a tail strike, at 1:19 in the video, due to overrotation.

With the help of the clearly visible livery (Royal Air Maroc), registration (CN-RNV) and approximate time (before August 2016, probably not by too much), I managed to find the specific Incident: Royal Maroc B737 at Frankfurt on Jul 23rd 2016, three takeoffs for the price of one on The Aviation Herald. It even links to the very same video that you do.
Unfortunately:

On Aug 30th 2016 the BFU responded to an inquiry by The Aviation Herald of Aug 25th 2016 stating, the BFU had neither received any notification by the crew, airline or airport involved nor by the person taking the video (see below) and became aware of the occurrence only through the release of the video into the public more than a months after the occurrence. The BFU argued that as result it will not be possible to establish sufficient facts and evidence needed for a detailed investigation, hence the BFU decided to refrain from initiating an investigation.

So we won't have anything better than guesses anyway.
The article does speculate that the wake turbulence of the landing aircraft crossing above the runway just before might have affected it, but it was too close to the starting point and is unlikely to have this effect, so what remains is that the pilot flying started to rotate too early. There may be basically two reasons for that:

The pilot flying started rotating before appropriate speed was reached, or
they calculated lower rotation speed (Vr) than they actually needed.

The take-off procedure with the speed call-outs made by the pilot not flying is the same for every take-off, so the second reason seems more likely.
The rotation speed depends on weight, density altitude and flap setting. Inserting wrong weight is probably most common reason for this type of incident, but calculating for higher flap setting than they used is a believable option here too as they used rather low setting for the actual take-off.
It should be noted that the pilot realised their mistake and handled it correctly by lowering the nose back to let the aircraft gain enough speed first.

It looks like a case of the flight crew using an incorrect flap setting for the takeoff and calculated Vr.  Looking at the video, there was very little flap deployed though the LE flaps and slats were extended.  The airplane struggles to become airborne then settles back down on the runway after attempting to exit ground effect.  The crew apparently realized the airplane wouldn’t fly, so the allowed to to remain on the runway, gain additional airspeed, then rotate and fly off when there was no alternative left.  Major safety violation there and could have caused an accident.  Fortunately there was ample runway to do so on.

I seem to recall several 737 pilots stating after this incident that this is the "flaps 1" configuration for a 737 and that it's a perfectly valid takeoff configuration. Though you're right that it might not be the configuration for which they calculated Vr.


text:
Is a supertransporter considered a different aircraft type than the one it is derived from?
By supertransporter I mean the SuperGuppy (derived from the Stratocruiser), the B747LCF dreamlifter, the A300-600ST, the airbus beluga XL, and any other aircraft whose role is to transport so large pieces that its cargo bay is way larger than the fuselage of aircraft it is derived from (I don't even know if my short list is exhaustive).
The answers of the question How are evolution and variants of aircraft considered by certification authorities? highlight that variants of an aircraft are considered as simple modification of the first type. In the case of super transporters, I imagine this is the same but:

aerodynamic obviously differs (may be especially relevant for rudder authority and engine out on take off scenario)
pressurization systems may differ (I guess those aircraft are not pressurized as airliners)
structural strength and command transmission are affected (cockpit shift, cabin floor in which cable may run suppressed, ...)

Those modifications are heavy and can affect all flight phases.
Given the Beluga XL (resp. the B747 LCF) is basically an A330 (resp. a B747) with modifications, does it share the same type certificate?

Such aircraft require separate certification. The Beluga XL has just completed its certification process.
From the Wikipedia articles you linked to:

The 747 LCF was granted FAA type certification on June 2, 2007.

and

Following a total of 335 flight hours being performed during the test program, restricted certification of the type was awarded by the European Aviation Safety Agency (EASA) in October 1995, enabling the A300-600ST "Beluga" to enter service shortly thereafter.

and

The Beluga XL made its first flight on 19 July 2018, and received its type certification on 13 November 2019.

I feel like an idiot not having search on manufacturers' website before asking. When Wikipedia speak of certification, it tend to be unclear if this is a new type certification or certification of only modified parts


text:
Why did my flight climb so sharply on takeoff?
I was on a Ryanair flight this morning that seemed to perform an incredibly aggressive takeoff from London Stansted on a 737-8.  Takeoff was fairly fast, but the climb was the steepest I ever encountered.
For context, we were taking off from runway 22, with wind 34 kt from the South/Southwest gusting 51 kt

Perception is one thing, but in reality the flight is very unlikely to have been much different from any other flight. Modern aircraft operate within quite limited ranges of performance so there really is very little room to change how a takeoff is done from flight to flight.

Sure, I had no objective data, but it felt insane and people were getting upset. I'm guessing as @deltaLima said, the wind added a lot of welly

It’s hard to judge how aggressive the actual takeoff was from this data. One contributing factor to the perception of aggressiveness is whether noise abatement procedures are required at Stansted. Pilots may be required to fly higher than normal Traffic Pattern Altitude as quickly as possible. Another factor is the 50 knot headwind. If this was surface or low level wind, it would affect the angle of climb. You would get to altitude in a shorter horizontal distance.

It looks normal to me. I look at flight radar all the time, and I’m about 2 hours east of San Francisco. I’m right before the mountainous terrain. I see flights that are currently above me and say “departed 9 minutes ago” from San Fran intl, and they’re well above 25,000FT at this point. I’ve even seen some that are already in cruise.

I assume you meant to say a 737-800 - the 737-8 hasn't returned to service yet.

If you flew in a 737-8, that was indeed aggressive, since they're currently still grounded worldwide and are likely to continue to be so for the next few months at least.

Note when your flight took off we were in the middle of what has been reported as "Storm of the Century" (By UK standards, anyway).

@Jamiec Agreed, this is probably related to the weather conditions which is somewhat covered by DeltaLima's answer.

I live and work in Cambridge, about 30 miles north of Stansted.  There's a major air museum about halfway between (at Duxford), just off the motorway connecting Cambridge and Stansted.  The motorway has been closed since last night because the wind has seriously damaged a hangar, and there is a high risk of large pieces of hangar (and potentially the exhibits!) getting blown into 70mph traffic.  It's been that windy.  The manoevre you experienced is commonly known as "getting the hell out of Dodge". :)

@JonBates What is "welly"?

@Michael I think it is an expression that comes from the Wellington boot. I  this context 'welly' is slang for 'a lot of energy', meaning basically it was given a good kick with the boot. But maybe the fine people at english.stackexchange.com can answer your question for you.

@DeltaLima spot on - it refers to the delicacy of control possible while wearing welly boots...

Datapoint only: Long ago I took the only flight out of NZ's notoriously windy Wellington (Rongotai) airport when a very major storm closed all sea, air and road (even) access for some days. I'd booked on multiple flights all day and each was then cancelled outright (rather than delayed as usual) and being on hand had managed to book the next flight, alo without success . At about 8pm they said one flight MAY get out. ...

... We walked to the aircraft (airbridge otherwise always used at Wellington).  The pilot advised that he would sit at the end of the runway and wait and if an opening cam take it ! :-). He advised it would be a very rough ride in the circumstances. He did not mention steep :-). Go! Funnest aircraft ride I ever had. It felt near vertical (an illusion) - I have been in 100++ commercial flights and nothing else ever came close. We gained the impression of almost lying back in our seats. Nonbody complained, given the circumstances. Sole aircraft out in days. Maybe he was a Ryanair pilot :-).

Go fly a kite. Not being cheeky; I mean that quite literally - go fly a kite and you will realise immediately what was happening. The headwind is increasing with height, therefore lift and so rate of climb increases with altitude. This leads to the dramatic swoop up into the air that is characteristic of kite-flying and your flight, apparently.

@OscarBravo If that's the case, why didn't it stall?

@Cloud The answer below from DeltaLima says it all. I just wanted to summarise it (wind varies with height) and get in the fly-a-kite joke. I guess it didn't stall because if the airspeed increases you can increase the AoA.

Your flight took off during a storm. During a storm, the wind speed close to the surface of the earth is much lower than the wind speed a bit higher up. This variation of wind speed over a short vertical distance is called wind shear. The aircraft is taking off into the wind, so during the initial climb the headwind increases. Increasing headwind during climb does miracles to the climb rate.
Suppose you want to climb from sea level to 2000 feet while increasing the true airspeed from 140 to 160 knots (70 m/s to 80 m/s).  In steady wind conditions that means the aircraft needs to accelerate 20 knots during that climb, which consumes part of the energy available from the engines.
But if there is a windshear and the headwind is increasing by 30 knots during that climb (not unreasonable in stormy conditions), the ground speed will reduce by 10 knots. Instead of needing to add kinetic energy, the aircraft needs to reduce it by converting it into potential energy (altitude). This means more energy is available for climbing and thus the climb rate is higher.
The wind reports from the airport at the time of take-off showed a wind of 29 knots (39 knots gusts), almost straight down the runway.
If you look at the wind profile this morning (I could not access yesterday's data anymore) you see that the wind increases from 20 kts at the surface to 51 knots at 3000 ft. That's a lot of free airspeed the aircraft gets during climb!

 source: screenshot from windy.com

 source: screenshot from windy.com
In addition, the effect of a stormy headwind is that the ground speed is relatively low. This makes the climb much steeper than in the no-wind condition.

Looking a bit closer at the raw data from FR24, the aircraft took off at 131 knots groundspeed (the first airborne report is 25 ft above the runway). 6 seconds after the first airborne ADS-B report, the altitude had increased by 525 ft. Even if we conservatively assume it took 7 seconds to climb to 500 ft (round-off errors), it requires a vertical acceleration over 1.6 g to achieve that. That must have felt very aggressive!
The first 2000 ft of climb took only 25 seconds, an average of 4800 ft per minute. The ground speed reduced to 119 knots by the time the aircraft had climbed 2800 ft, 37 seconds after take-off.
After that, the aircraft had climbed through most of the boundary layer of the earth and the windshear reduced. The rest of the climb was fairly typical.

It was not only your perception; by all means it was an impressive take-off performance for a B738

Superbly explained post, thanks!

Right, until that wind boost proves temporary and reverses, at which point it does miracles for sink rate.

So why don't storms / strong winds (such as this case) cause aerodynamic stalls more often (and consequently lots of.. incidents?)

See my comment below for why it does not cause stalls fir the big jets.

And another comment here- the aircraft is very light, probably taking off into a storm- so its a major factor as well.

I think can just imagine a Ryanair employee going "heck yeah" when thinking of all the fuel saved when he heard about the storm. (And also someone else thinking just the same for environmental reasons...)

Sometimes a departing airplane will receive or be offered an accelerated climb profile from ATC which gets it up and out of the published approach and departure patterns quickly. If the pilot elects to take the profile, the resulting climb will be unusual, and spectacular.
I was on a Rockwell SabreLiner departing from San Jose, Ca in a very lightly-loaded condition some years ago when the pilot was offered this, and he took it- and warned us about how steeply we would be climbing. I was in one of the rearward-facing seats and looking backwards out the window next to me I was treated to a stunning view of downtown San Jose below us while basically hanging from my seat belt during our climbout.
It was fun.

It appears that it took the pilot about 15 mins to climb from near sea level to FL370.  That's a climb rate of about 2500 feet/min, which is a pretty modest climb rate for a jet.  If you're looking for fast climb rates in a transport, check out Lear 35s.  If given an unrestricted climb to cruise altitude, they will often do 5000+ feet/min!

Good point, Carlos. Way to do the math on that one. I think most of us were focused on the OP’s subjective perception and not on the raw numbers. Always trust your instruments (and verify with a cross check).

Looking at the climb to FL370, everything seems normal. Looking at the climb to 2000 ft AAL which only took 25 seconds, you see the rate is 4800 feet/min on average after leaving terra firma, with 500 feet climb in just the first 6 seconds. That is impressive for the B738.

I don’t see anything out of the ordinary here.  They may have executed a more aggressive climb but it’s well within the 737’s capabilities.

@CarloFelicione being within the capabilities of the plane does not define whether it was normal or not - and 100ft/s is not normal!

makes me wonder what newer Learjets like the 60 or the 75 could do on an unrestricted climb.  I know they are bigger, so even with more powerful engines that characteristic could change.

A bit more elaborated answer gathered from my comments above:
First of all- what do you mean by aggressive- Shaky? fast? high pitched?
If the headwind is stable- it changes the Ground speed at which the plane rotates, making it lower. After that, the aircraft climbs at the same pitch angle as always, once it transitioned to the stage of acceleration from V2. What does change a lot is the rate of climb per distance, nor per time. The situation is different if it is gusty- then the scenario is that it's all very bumpy, and planes do trade a bit of speed for pitch due to the logic of the aircraft flight algorithm- constant thrust, changing pitch. It will be elaborated further down the answer.
If it's unstable at low alt, maybe they maintained a high pitch, low speed, flaps down climb to clear the turbulent air (they just maintained a lower speed all the way out of the boundary layer). Finally, maybe they performed a full thrust take off- which is sometimes performed when wind shear is predicted, resulting in a very steep pitch after take off for such a light plane (1-hour flight).
If the wind changes and adds additional 30 knots of headwind in an instance- and stays there- meaning another stable mass of air- the pitch will become higher but only until the aircraft loses the energy it gained from the pitch up- after which it will retain it's original attitude and continue climbing with the same rate of climb- because after some time the pitch angle wouldn't hold the speed as the aircraft transitions to flying in the new "air mass".
Elaborating on the concept of fixed thrust: These aircraft are built in a way that they maintain a uniform setting of thrust throughout the whole duration of the climb, decided after their performance calculations. Meaning- if there is a change in a headwind- they will pitch a little bit higher. This is possible due to the logic of the machine that rotates and keeps a velocity higher than V2, which is the safe airborn speed- meaning there is a margin.
Next: as for sudden decreasing headwinds- the aircraft always corrects it's pitch accordingly, and they are not as edgy as little light planes. Finally- the pilots can always lower the nose or apply more thrust or both. In addition- when conditions prevail that dictate the usage of wind shear conditions in the calculations- the aircraft is rotated at a higher velocity than the normal V2, giving it further margin, and they usually use flaps 20 (or the equivalent in an airbus which I am not familiar with) in order to support further fluctuations in wind speed. All in all- the aircraft has margins.
As for the actual technique the plane maintains pitch- I would assume that it has its barriers and the fluctuations in attitude are gentle enough in order not to get to high or low exactly for the reason you mentioned above. If you maintain a constant pitch attitude- you can also exceed the flaps speed. Final note- when encountering a real wind shear- 15 knots deviation, 5 degrees of pitch fluctuation, 1 dot of GS deviation, 500 FPM vertical speed deviation, the pilots would engage the wind shear maneuver- meaning TOGA (initiating a sequence of actions that are built to sustain a wind shear situation), full thrust to maintain possitive vertical speed until clear.
I hope this is not too technical, will be happy to explain everything.
I you understand the reason the aircraft acted the way it acted- maybe you will be able to point out exactly how it felt.

Thanks.  I'm a (lapsed) PPL(a).  To answer your questions, its hard to remember exactly, but the perception was of a steep, high-g climb-out with low-moderate turbulence.  The exact timing is more subjective I'm afraid, and I forget whether it was immediately after rotation, or a little later on, but it lasted maybe 10-20 seconds

So my guess would be full thrust TO, with flaps down climb to a higher altitude to escape all the winter down closer to earth. But again- only a guess.

It was due to the wind shear. Wind shear creates a vector gradient. If the vector gradient direction is upward in the head you'll get additional vertical force for lifting and its magnitude is larger than the downward force in the tail. That's why it's called wind shear because the wind applies a shear force to a flying body (in this case airplane). That's will happen only when the high-speed wind is heading towards your plane and your plane take off with a rotational velocity (Vr) designed for a steady condition. As force can be modeled as a rate of change of momentum over time it makes sense that you get a sudden steep climbing pattern because the momentum of your plane has been increased.
Wind shear is classified as an atmospheric disturbance. Therefore, it is correlated directly to the flight qualities. You can check the table in Flight Dynamic Principle Chapter 14 to see the relationship. As long as you can maintain control there will be no problem. For the passenger's complaint, they have the right to complaints as a part of the whole system. A complaint is a gift to improve the overall system the airlines, the pilot skills, and the aircraft manufacturers.
The only thing to be concerned from your case is communications. You should get a weather report before take off. Someday, this communication issue can be reduced by visualizing the wind. I guess everybody would be happy if we are able to see the wind shear. Some airports have the technology to visualize wind shear. It's just the implementation of the Tyndall effect (at least for a while). Maybe in the future, everyone will able to see the wind shear using 3D light technology. The plasma emission technology is the one and only 3D light that we have today and it's dangerous. The plasma emission phenomenon near the cloud full of static electric charge will transform your Airplane to a giant spark plug. For now, just trust the pilot they're trained well. If you're a pilot just trust the aircraft manufacturers they've been work so hard to keep everybody safe and of course, communicate well with the ATC & ground staff.

Only your first sentence has something to do with the question, and saying "it's like someone else said" is not really an answer. The rest is totally unrelated to the question.

@Bianfable thank you for your constructive comment. I already edit my answer according to your comment.


text:
How much fuel can be saved in a half full of passengers plane?
On a typical airliner (let's say A320 / B737 / or similar), comparing a plane full of passengers vs one half full, how much fuel an airline can save on a trip when the plane is only half full?
(This is assuming both cases will accomplish the same mission, distance, time, etc.)

Related (maybe duplicate): How much does it cost extra to fly with one additional passenger?

define "save". sure, you use a smaller total amount of fuel, but you still need the fuel to move the same size aircraft, so the fuel per passenger goes really high, making your efficiency worse.

@Federico I see your point, but i mean just the fuel alone, just that. How many pounds of fuel they would have to purchase in one case vs the other.

Highly related, but with 80% instead of 50% payload: How can I calculate the fuel consumption of an Airbus 320-200 at various loads?

Be aware sometimes airlines bring more fuel than necessary, because it costs less to carry the extra-weight than to buy the same quantity at the destination airport (tankering).

@mins thanks for bringing that point, I was suspicious something like that was done by airlines but wasn't sure.

The most can be saved with short range planes on long trips. When passenger load is around 10% (as it is for very long range airliners), reducing that to 5% will not make much of a difference. But we can do better than that.
If you want a good estimate, the venerable Breguet equation will already give good results. First we need to know how much of a difference halving the payload will make: The average mass of a passenger plus baggage for short-range trips is 100 kg.
If we use an A320 with 180 passengers on a short trip of 1000 km as the basis, the zero-fuel mass would be OEW + 18 t = 60.6 t in the 100% case and 9 tons less in the 50% case. Allow for 2 t of fuel reserves and plug that into the Breguet equation, using a fuel burn of $b_f$ = 0.000018 kg/Ns and a speed of Mach 0.78, which equates to $v$ = 262 m/s in 11.000 m altitude:
$$m_1 = m_2 \cdot e^{\frac{R\cdot g\cdot b_f}{v\cdot L/D}}$$
The L/D should be 18 and for the range we use R = 1000.000 m. $m_1$ is take-off mass and $m_2$ landing mass. This gives a fuel need of 2387.5 kg for the 100% case and 2044 kg for the 50% case. To be realistic, you would need to include different fuel flow during climb and descent, but the real value shouldn't be too far from the results we get from the Breguet equation. Halving passenger load only saves 343 kg or 3.8% of the reduction in payload on a short trip.
Now we repeat the calculation for the maximum range of the A320 of 5,700 km. For the 100% load factor case, take-off mass becomes 77.5 tons, which is just shy of the 78 tons MTOW of the A320. Covering 5700 km with 180 passengers will consume 14887.5 kg of fuel while doing the same with only 90 passengers will consume 12747 kg or 85.6%. This is 2140.5 kg less or 23.77 kg per passenger.
If we now do the same calculation for an extreme range like 12.000 km in a Boeing 777 or an Airbus A340, we cannot fill all seats because so much fuel needs to be taken onboard.
What can be saved, therefore, varies between 4% and 15% of the reduction in payload, details depending on passenger mass fraction and range.

The answer is heavily dependent on the exact airliner. As a general rule, the practical answer is "not enough".
Reducing the airliner's weight saves fuel during takeoff (slightly), climb (linearly) and cruise (linearly). But it doesn't save fuel during taxi and landing, which comprise a meaningful proportion of fuel burn for short flights.
According to this NASA report, incremental fuel burn ranges between 0.002 and 0.007 gallons per lbs per hour. Tossing out the outliers, 0.004 appears to be the middle value. For 100 pax at 200 lbs each, that's 80 lbs/hr. For a 737 or A320 burning 800-1000 lbs/hr, this is 8-10% of their overall fuel burn.
In conclusion: flying with only half the passengers takes about 10% less fuel.
Large airliner operators - A320 and up that can take containers, and especially A300 and up that take AKEs - will try to fill the remaining weight limit up with cargo if possible.

Thanks Therac. Why it wouldn't save fuel during taxi? Don't you need less power(hence less fuel burn) to move an half full airplane trough the taxiway than a full airplane?. Or  the difference would be just too minimal?

@Gabe When the engines run at idle, most of the fuel is spent just spinning them, not doing any useful work. Taxiing has an efficiency of less than 1%.


text:
Which civil aircraft use fly-by-wire without mechanical backup?
Though almost the whole Airbus 3XX family uses fly-by-wire technology, it also has mechanical link/manual backup for the rudder/elevator trim as explained here.
On the military though, my understanding is that the F-16 is fully fly-by-wire (no mechanical backup).
Are there any other aircraft on the civil aviation that are full fly-by-wire?(no mechanical backup)

If you mean airplane, then say it. Aircraft includes UAV, which is FBW by nature.

FBW implies flight computers determine which surfaces are used and at which amplitude, from pilot orders, offering. a flight envelope protection. "Not FBW" just means the pilot orders are not interpreted and there is no protection, but orders can be sent to the surfaces using wires. On A320, THS mechanical linkage is a backup, in addition of THS FBW. Note the THS trim wheel spins by itself when FBW is active, because of the mechanical linkage feedback of FBW actions.So your question is about dropping the existing mechanical backup, the FBW feature is already in place.

@mins Disagree, as does https://aviation.stackexchange.com/questions/89151/what-is-the-difference-between-autopilot-and-fly-by-wire-system. FBW removes the mechanical interface to flight surfaces and instead sends signals to control surface actuators over electronic wires. This enables envelope protection and other computed actions. Having a mechanical backup to a mechanical primary makes no sense outside military applications that expect damage.

@user3528438 and @ mins I have updated the title.

@Pilothead: "FBW removes the mechanical interface to flight surfaces and instead sends signals to control surface actuators over electronic wires": I don't understand what you mean. It seems clear from this schematics FWB computers (ELAC and SEC) control the THS actuators via electronic signals, and at the same time there is a direct mechanical linkage between the THS and the trim wheel (same for the rudder, FAC vs. pedals).

A220 nee Bombardier C-Series is full FBW with no mechanicals. It's about the most advanced of current airliner designs.

Airbus
While the Airbus A320, A330 and A340 still have fly-by-wire with some mechanical backup, the Airbus A380 and A350 removed these. They are full fly-by-wire using electrical backup for hydraulically controlled surfaces:

The A380 introduces the following major evolutions:

Suppression of all mechanical backup controls.
These are replaced by electrical backup controls.
Addition of a new pitch trim switch, that replaces the
trim wheels due to the deletion of the mechanical pitch
trim control. [...]
Introduction of Electro-Hydrostatic Actuators (EHAs)
and Electrical Backup Hydraulic Actuators (EBHAs) in
order to delete one hydraulic circuit.

(Airbus A380 - Flight Deck and Systems Briefing for Pilots - 8 Flight Controls - 1 General)

The A350 flight controls system benefits from evolutions
introduced on the A380: [...]

Replacement of all mechanical backup controls by
electrical backup controls
Addition of a new pitch trim switch which replaces
the trim wheels

(Airbus A350-900 Flight Deck and Systems Briefing for Pilots - 12 Flight Controls - 1 General)
Boeing
Boeing also removed the mechanical backup found in the 777 fly-by-wire system (see Why does one of the Boeing 777's spoilers deploy differently from the rest?) on the 787, which uses electromechanical actuators (EMAs) instead:

For example, EMAs are used for landing gear braking, mid spoiler surfaces, and trimmable horizontal stabilizer on Boeing 787.

(A review of electromechanical actuators for More/All Electric aircraft systems)

787 Fly-by-Wire Flight Controls
All Surfaces Fly-By-Wire

Eliminates cables [...]

(787 Systems and Performance)
Bombardier
Bombardier designed the C Series (now called Airbus A220) without mechanical backup as well:

There is no mechanical connection between the flight deck flight controls
(sidestick controllers (SSC) and rudder pedals) and the aircraft control
surfaces (ailerons, elevators and rudder). The FBW system transmits
commands to the hydraulic actuators to move their associated flight control
surfaces.

(Bombardier CS300 / Airbus A220-300 FCOM Vol. 1 - Flight Controls - Fly-By-Wire System)

The mechanical rudder backup was actually removed on the A340-500 and -600, and spread to newer A330s and A320s.

@user71659 Good point, but I think they still have a mechanical link to the THS, correct?

The Dassault Falcon 7X and later are completely fly by wire with no mechanical backups.

The Gulfstream G650 (and beyond):
https://www.aerospacemanufacturinganddesign.com/news/parker-aerospace-flight-controls-11112/


text:
How flexible are small airplanes wings compared to airliners?
When talking about flexible wings, it always comes to mind big airliners like the 787 or the A350.
But knowing that flexible wings help reduce the flight bumpiness and small airplanes are known for being more bumpy, I wonder how flexible is the wing of a typical modern day GA airplane like the Cirrus SR22 vs a modern day airliner like the 787?

All wings are flexible, if they didn't flex they would break! I'm not entirely clear what the question is here.

Like how flexible are they compared to a 787 wings for example. Updated title.

What are you actually asking here? If you want to know why airliners are less bumpy than light aircraft then the principal factor is the overall mass of the aircraft including payload and fuel. If you actually do want to compare the structural stiffness of the airframes then I suppose one could come up with something that expresses displacement per unit force (like a Young's modulus, if you will), but I doubt that would tell you very much given the vastly different sizes of the airframes involved.

They all flex to some degree where some or all of a wing is cantilevered from the fuselage, or outboard of a strut, anywhere there is a beam in bending supported at one end.
Cruise along in a fabric aircraft with wood spars, like a Citabria, in bumpy air and you can see the outer part of the wing beyond the strut flexing up and down enough to be obvious (maybe up to an inch at the tip if the G load is high enough). It's not enough to affect ride quality noticeably though.
On a glider or motorglider with cantilevered wings with long spans, they flop around quite a lot (maybe 6 inches to a foot at the tip). On sailplanes with very long spans and low wing loadings, the flex makes the ride much more pleasant at high speeds compared to a glider with very stiff spars.
So, wing flex does enhance the ride in bumpy air in gliders and motorgliders, and possibly somewhat on the latest composite airplanes, but generally not enough to notice on most light aircraft.

A very important consideration to your question is the mass of the fuselage.
Modern airliner wings may be way less flexible on a foot per foot basis than light aircraft wings, but they are longer.

However, there is a much greater resistance to movement (inertia) with a heavier fuselage.

As a result, when a gust hits the aircraft, smaller aircraft will tend to move (as a whole) rather than bend their wings.  With larger aircraft, it's the opposite.
Another consideration is the smaller surface area to mass ratio of larger aircraft.  A ride on a paper airplane will certainly be bumpier than a 747 in gusty winds.
To summarize, in response to a gust, the resistance to  bending torque
on the airliner wing may be within a degree of magnitude to a GA aircraft, but the aircraft mass differential is on the order of 2 degrees.  The airliner is easily 100x heavier than the GA aircraft.
Just like riding in a big Cadillac vs a go-kart, the bumps in the road are felt way less in the Cadillac, even though the suspension may be slightly stiffer.

don't you mean the opposite on your second paragraph?

Second paragraph edited.


text:
What's the average flight distance on a typical single engine aircraft?
Statistically what is the average distance traveled per flight by a typical single engine aircraft. Since there are many types and sizes of single engine, ideally I want to limit this to small single engine aircraft like the Cessna 172.
In other words, aircraft with this conditions:
-Single engine
-Unpressurized
-4 seats max
NOTE: The average must be from flights from point A to point B only, in other words, for example flights for training in the airport pattern should be discarded.

Nobody keeps statistics on stuff like this.

Can it be estimated from something like flightaware.com logs, at least for ADS-B equipped airplanes?  Exclude flights that are too high or longer than a Cessna's range.

Average will be such a meaningless metric. The flights by a school aircraft will vary considerably from the regular tourer/commuter.

Considering the high fraction of single engine aircraft used for training, the median distance of all their flights is probably 0.00 miles - landed at the same place they departed. Once you start adding conditions, this becomes a request for somebody to run a database query (on a database of unknown existence, completeness, or quality) for you with a bunch of parameters you've specified. Not sure I see much value in such requests.

@CamilleGoudeseune how can I do that?

@Gabe I don't know how to get such data.  Even if that's hard, I still guess that there's no easier or more accurate way.  Also, as others have noted, such flights represent distinct populations that shouldn't be lumped together.  Try to define a subset, e.g. $100 hamburger run.

You'd have to do a pilot survey of cross country flights and calculate an average from the results. I'd guess about 100 miles would be a broad average, if you figure most cross country legs are 30 minutes to 2 hours.

Thanks @JohnK, I think the 30 minutes/2 hour leg input could be useful to do a simple estimation on distance. I also think the data is already there as Camille said, is just a matter of filtering, and now that you mention time I noticed FlightAware also tells you the time from takeoff to landing and also the total distance when you click on the aircraft icon. So, the data is already there all I want is to filter by single engines(which they have the ICAO type code and can be used to tell you if is single engine).

@RalphJ median won't be 0 for distance. Displacement median might be 0 but distance median cannot be 0 without negative numbers in the range.

@AadirajAnil What's the median of the following sequence: 0, 0, 0, 0, 50, 200, 500? You don't need negative values in the sequence for the median value to be zero.

Yeah but distance won't be 0 right? So where will the zeroes in that sequence come from? If an object moves, it can't travel zero distance because the actual length it travels can't be zero.

@FredLarson per flight. I've updated the post description.

https://www.reddit.com/r/flying/comments/vlj58b/whats_your_average_flight_distance/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button
anyone saw this?

@Gabe  -   and everybody....  so basically what we are saying, here, is that given everything else, YMMV...  Perusing Aadiraj Anil's reddit link, most of those folks seem to be discussing long trips of generally several hundred miles...

507 miles is the mathification of JPE61's reference with a boatload of implied assumptions:
3.5m - General aviation and part 135 total landings single piston engine fixed wing 1-3 seats.
13m - General aviation and part 135 hours of use single piston engine fixed wing 1-3 seats.
3.7 - Hours per landing
137 - Average mph of single engine aircraft
Thus: 507 - Average miles traveled per landing

Over 3 hours per landing on average sounds extremely high, even discarding pattern work in trainers. The maximum endurance for a lot of single engine aircraft isn't much higher than that, and for every 30-minute flight, you'd need a 6+ hour flight to balance that out to get the 3.7 hours number.  And those would be rare, compared to how often the planes would have the much shorter hops. (After all, if you need to travel 500+ miles, doing so at ~137 mph isn't the most pleasant way to get there.) I'd suspect something leading to that 3.7 hours value is way off-kilter.

Thanks @RalphJ for your comment, I was going to say the same thing, but as OP I didn't wanted to sound like I'm being a pain in the *.  I think essentially the data source used  for the answer is not the most ideal for my question. As I said in the comments at the OP, the data is already there on flightaware (it tells you the distance and the time flown whether it was VFR or IFR flight) or other similar websites. All is needed is to filter by single engine(which can be determined by the ICAO type designator, which is also in the data) and aircraft takeoff and landing point (also in the data).

@RalphJ pretty much what my Stetson-Harrison indicated, and hence I didn't want to calculate any further. I do think that given the situation, Camille's approximation is very good.

@RalphJ That is what the data said. You claim that it is way off but don't have anything more than opinion for support, so let's see some data.

"That is what the data said."  But you also said:  "with a boatload of implied assumptions"  So what are the assumptions?

@MichaelHall I'm not sure I understand the point of your comment. This is a simplistic calculation based on survey data, do you not think assumptions are required? The time and landing data is 6770 opinions of pilots who fly these aircraft. Ralph said this was all wrong, that is one opinion, so I thought he ought to support his statement. I added the speed of small aircraft and applied it to the entire operating time, which is obviously inaccurate as it does not allow for ground operations or climb. Pilots probably got time from a annual hobbs meter check, so it likely is maintenance as well.

I'm simply asking you to state the assumptions you used to come up with your answer.  Is that a fair request?

Here's a thogt -  avg flight distance 300 to 350 miles; time in flight at 137 mph = 2 to 2.5 hrs...

The average distance flown by the host of singles is going to depend on what one is doing when taking such a flight and who owns the plane.  Is this a rental plane, or is this an owner flight? If we assume a majority are likely to be owner operated, is this plane a hanger queen most of the year, or is it regularly flown? Whatever the circumstances, are we going out to lunch to get a $100 hamburger?  Or is this a business or pleasure trip to a more distant location?
Speaking from experience, the hamburger flight is usually less than 150 miles.  But if we take an estimate based on the POH noted range of the 172, at an average that may be about half the range, or about 300 to 350 miles, more or, most probably, less. Why this number?  Pilots taking such day flights are generally loathe to pay for more fuel than they will use as they do not want to leave more money in the tank than necessary. Further, if they are smart, they do not want to risk fuel exhaustion, as this will likely terminate their flight career.  If we assume this plane is flown regularly, and not subject to interminable storage, the fuel cost is not likely an issue.  But if this is a rental plane, or a plane that is stored indefinitely, then we can assume fewer flights by the same pilot, and a pilot-average flight distance about half the range, more or most likely less.
On the other hand, an executive pilot owning a single-engine piston-powered aircraft may routinely fly 400 to 600 miles on a one-way out trip.  One such pilot known to me routinely flies this way in providing services to the engineering firm having the FAA contract for airport maintenance and upgrade.  Consequently, they are almost always flying to an airport with services at which, thereupon, they may fill up. In his case, about half the range would be about 450 miles. Assuming 3/4 full for the flight home, this would leave the plane 1/4 full at the hanger to be readied for the next flight.
So this is going to depend on plane ownership, reasons for the flight, and general use of the aircraft.  Consequently, without actual data (which may be hard to acquire in a specific manner), we are left to assume an estimate.  Consequently, being left to rely on assumptions where anything seemingly unique is actually one out of probably many, our estimate being half the range is probably close to the average, more or less.  For the 172, depending on the model, that is about 300 to 350 miles.

I will leave the analysis part for you, but the best source of data is here:
https://www.faa.gov/data_research/aviation_data_statistics/general_aviation/cy2022
The average distance of A to B flights is not listed, and the category closest to your specification is SEP 1-3 seats, but I guess that would be close enough.
Best approximation for avg distance would be to calculate avg hours flown with a flight plan (IFR+VFR) by the aforementioned plane category  (that would be about 32h), and then figure out from other tables how many total operations that category of planes has and work towards number of operations/aircraft/planned flight. You should be able to get a pretty  good Fermi estimate (or better) by then taking into account avg cruising speed and substract ~30 minutes of flight time per operation for taxiin.
Sorry for not doing the math for you, but I've had a pretty sciency week already, so I'm done with braining right now.
You can post your results here as an answer for peer reviewing.
Please feel free to not give points to this answer, since it only reveals data source and method, not the answer itself.

We can do some back of the envelope math to work this out. Most Cessna 172s use a variation of the Lycoming O-360 four cylinder engine. Aircraft engines have to be overhauled on a regular schedule. When an engine gets overhauled, the major components are pulled out and sent to Lycoming to be tested. Some parts are replaced, others are mixed in with a pool of identical parts. When your engine is overhauled, it can be considered a "new" engine. In an ideal world, in a well-maintained aircraft, the engine can be overhauled again and again until the plane crashes or the cost of overhaul gets too high to be worthwhile. So let's consider "an engine" to be one set of parts, and when an engine is overhauled, that's a "new engine".
Lycoming's service instructions are found here: https://www.lycoming.com/sites/default/files/attachments/SI1009BE%2520TBO%2520Schedule.pdf
Specifically, the time between overhaul for an O-360 is 2000 hours.

A Cessna 172 has a cruise speed of 125 mph. For the sake of simplicity, we can simplify the life of a Cessna 172 to either moving at cruise speed or not moving at all. For the sake of the argument, I'm going to estimate a 172 spends 80% of its life at cruise speed and the rest idling on the ground (this will vary a lot based on how this particular plane is being used, but I think this is a good starting point).
2000 hours * 0.8 * 125 mph = 200,000 miles.
I think it's reasonable to say a Lycoming O-360 engine might travel about 200,000 miles between overhauls.

I am not sure but I think he is asking about the avg single flight distance of a Cessna 172.  Not the distance it covers between overhaul

I appreciate your answer Chris but my question is referring about distance per flight

If there is any information in terms of total number of overhauls done for a country/region and a known number of airframes in that region it would be possible to approximate total distance flown, though still leaves questions how many flights that is made up of.

Oh, I turned the question around in my head. "Average flight distance on a single aircraft engine". My mistake.